Cane Sugar and Yeast

Today I was reading “Brewing,” by Alfred Chaston Chapman and came upon this morsel:

Cane sugar itself is not directly fermentable but is first converted by the enzyme invertase contained in the yeast cell into invert sugar which then undergoes decomposition into alcohol and carbon dioxide. Cane sugar may therefore be directly employed as a brewing material but inasmuch as its use is thought by many brewers to conduce to yeast weakness it is more usual to employ the invert sugar made from it. On the manufacturing scale the invert sugar is prepared by heating a solution of cane sugar with a small amount of a mineral acid until the desired change is complete. The acid is then neutralized and the solution after more or less decolorization is evaporated in a vacuum pan to the consistency of a syrup. In this process the cane sugar undergoes hydrolysis and is converted into a mixture of dextrose and laevulose in nearly equal proportions which is known as invert sugar. The change may be represented by the following equation:

C12H22O11 + H20 -> C6H120 + C6H1206

Cane sugar + Water -> Dextrose + Laevulose = Invert sugar

As used by the brewer invert sugar is a product closely resembling golden syrup in appearance and in flavour but when allowed to stand for some time it sets to a soft solid mass owing to the crystallization of the dextrose the laevulose which crystallizes only with great difficulty remaining in the syrupy condition. The commercial syrups usually contain about 75 per cent of invert sugar the balance consisting of water with small quantities of cane sugar and a little mineral matter. In its composition therefore it is very similar to honey.

This got me thinking about making invert sugar from cane sugar any time I might normally add straight cane sugar. Though of course it would be easier to just buy candi sugar, but where is the fun in that? This post has a good description of the process. Essentailly the steps are:

• Boil water
• Desolve Cane Sugar
• Add acid (lactic, lemon juice)
• stir
• chill

Again, check out this post for the detailed method.